I wanna be the Best Guy
The strong point of the game are clearly the bosses. They're remind me of the bosses in Time Machine (Extremely pattern-heavy, requiring the use of blind spots once in a while, as well as some quick-damage strategies), but not as good-looking (Aside from Gustav, perhaps). There are traps after you beat the bosses, but honestly, I don't really count it as a negative thing, that just means you get to enjoy the fights yet once again. Autofire is enabled in the game, so being unable to mash isn't an excuse.
Gustav and Tor are by far the best bosses in the game. Tor is the giant robot, and I'm quite surprised to see something Iji-related in a fangame. It features some attacks from the original Tor (Last boss from Iji), as well as some original attacks, and the best part, there are the background attacks as well. The epic music helps a lot. Some attacks might seem way too unfair, but you just need the right strategy. It's the only boss in the game that doesn't have a pattern, and he gets stronger as his HP gets lower.
Gustav is the last boss in the game, and he's really, really cool. His attacks, the music, the effects, the background and the tilesets, everything mixes up perfectly, in a way that is very rare in a fangame. This fight has an awesome atmosphere. But of course, the gameplay has to live up to it. And it does. It's a quite enjoyable fight, and the attacks are somewhat RNG-pattern-ish (They follow a pattern, but some parts of this pattern don't work the same way every time). In other words, this is a rather unpredictable boss, but still fair (With one exception for a combination of attacks that can give you impossible RNG), and surprisingly well-planned (Even though some attacks might seem like they give you more room to damage him, they actually don't). His intro is a bit too long, though. It takes so long that Gustav himself complains about it.
One warning, though: Don't keep Z pressed when you go inside a boss room, or you might become unable to shoot until you die (Or lose a lot of your shooting speed). It's an annoying glitch that this game has, I don't really know why.
Also, for those who don't know, the game DOESN'T END after the fight with the giant robot. After getting past the fake credits, you'll get back to the beginning, and the upper path will be unlocked. There are still a couple short stages until you get to Gustav. He is the true last boss.
I would say that surviving through the platforming is worth it for the bosses, after all, it's just bad, not incredibly bad (It could be worse). Would recommend it, as long as you can handle some annoying platforming.
World 1 - Garbage traps.
Boss 1 - Simple and pretty boring, trap at the end.
World 2 - Even more garbage traps.
Boss 2 - Even more boring than boss 1. Trap at the end.
World 3 - Still garbage traps.
Boss 3 - Based on Ao oni. Bad. It's not even a boss. I counted it as a boss because it gives you a crystal.
World 4 - Actually a stage with pretty cool-looking ambient imo, but still, platforming is bad.
Boss 4 - Actually one of the two good boss in the game. Cool attacks! However that final explosion trap is pretty mean, since this boss is actually quite a challenge.
After these (90% garbage) contents, you can watch the fake ending which has a death trap in the end. After you dodge it, you can progress further upstairs(which was blocked by the walls with crystal).
World 5 - Look, you still have a hope to platforming section? It's bad.
Boss 5 - This boss is pretty mediocre, but not bad. The only boss that is made of avoidances(You have to constantly shoot at it though).
Final World - Hey it's the final platforming! It might be sick and fun? No! It's the worst.
Final boss - The only boss with the name, Gustav. It's the pinnacle of this game. It's actually a well-made boss for me. I had a lot of fun when I was playing this game for the first time. Interesting fact : The portals he shoots at the second attack actually teleports you to the random death-spots in the game. You might want a save backup since you can be stuck in the middle of the game(don't tell me you want to do these platforming again).
After you beat Gustav, you have to get past the final garbage platforming screen(yeah...at least it's the final one) and watch the true ending. After the ending, there's actually a portal room that is accessible from one of the keys.
So overall, all of the platforming and some bosses are garbage, but Rot and Gustav boss made this game to 5.0.